ISOLATION AND CHARACTERIZATION OF DEHALOSPIRILLUM MULTIVORANS GEN-NOV, SP-NOV, A TETRACHLOROETHENE-UTILIZING, STRICTLY ANAEROBIC BACTERIUM

A strictly anaerobic bacterium dechlorinating tetrachloroethene (perch loroethylene, PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) was isolated from activated sludge with pyruvate plus PCE as en ergy substrates. The organism, called Dehalospirillum multivorans, is a gram-negative spirillum that does not form spores. The G+C content o f the DNA was 41.5 mol%. According to 16S rRNA gene sequence analysis, D. multivorans represents a new genus and a new species belonging to the epsilon subdivision of Proteobacteria. Quinones, cytochromes b and c, and corrinoids were extracted from the cells. D. multivorans grew in defined medium with PCE and H-2 as sole energy sources and acetate as carbon source; the growth yield under these conditions was 1.4 g of cell protein per mol chloride released. Alternatively to PCE, fumarat e and nitrate could serve as electron accepters; sulfate could not rep lace fumarate, nitrate, or PCE in this respect. In addition to H-2, th e organism utilized a variety of electron donors for dechlorination (p yruvate, lactate, ethanol, formate, glycerol). Upon growth on pyruvate plus PCE, the main fermentation products formed were acetate, lactate , DCE, and H-2 At optimal pH (7.3-7.6) and temperature (30 degrees C), and in the presence of pyruvate (20 mM) and PCE (160 mu M), a dechlor ination rate of about 50 nmol min(-1) (mg cell protein)-1 and a doubli ng time of about 2.5 h were obtained with growing cultures. The abilit y to reduce PCE to DCE appears to be constitutive under the experiment al conditions applied since cultures growing in the absence of PCE for several generations immediately started dechlorination when transferr ed to a medium containing PCE. The organism may be useful for bioremed iation of environments polluted with tetrachloroethene.